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[ValueTracking] Don't assume shift values are in range 

Reduced (as best I could...) from oss-fuzz #4857 test case

llvm-svn: 321634
This commit is contained in:
Simon Pilgrim 2018-01-01 22:44:59 +00:00
parent af35f5ec1d
commit 6720726d27
2 changed files with 25 additions and 4 deletions
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8
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -2264,9 +2264,9 @@ static unsigned ComputeNumSignBitsImpl(const Value *V, unsigned Depth,
// ashr X, C -> adds C sign bits. Vectors too.
const APInt *ShAmt;
if (match(U->getOperand(1), m_APInt(ShAmt))) {
unsigned ShAmtLimited = ShAmt->getZExtValue();
if (ShAmtLimited >= TyBits)
if (ShAmt->uge(TyBits))
break; // Bad shift.
unsigned ShAmtLimited = ShAmt->getZExtValue();
Tmp += ShAmtLimited;
if (Tmp > TyBits) Tmp = TyBits;
}
@ -2277,9 +2277,9 @@ static unsigned ComputeNumSignBitsImpl(const Value *V, unsigned Depth,
if (match(U->getOperand(1), m_APInt(ShAmt))) {
// shl destroys sign bits.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (ShAmt->uge(TyBits) || // Bad shift.
ShAmt->uge(Tmp)) break; // Shifted all sign bits out.
Tmp2 = ShAmt->getZExtValue();
if (Tmp2 >= TyBits || // Bad shift.
Tmp2 >= Tmp) break; // Shifted all sign bits out.
return Tmp - Tmp2;
}
break;

21
llvm/test/Transforms/InstCombine/udiv-simplify.ll
View File

@ -62,3 +62,24 @@ define i32 @PR30366(i1 %a) {
%d = udiv i32 %z, zext (i16 shl (i16 1, i16 ptrtoint ([1 x i16]* @b to i16)) to i32)
ret i32 %d
}
; OSS-Fuzz #4857
; https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=4857
define i177 @ossfuzz_4857(i177 %X, i177 %Y) {
; CHECK-LABEL: @ossfuzz_4857(
; CHECK-NEXT: store i1 false, i1* undef, align 1
; CHECK-NEXT: ret i177 0
;
%B5 = udiv i177 %Y, -1
%B4 = add i177 %B5, -1
%B2 = add i177 %B4, -1
%B6 = mul i177 %B5, %B2
%B3 = add i177 %B2, %B2
%B9 = xor i177 %B4, %B3
%B13 = ashr i177 %Y, %B2
%B22 = add i177 %B9, %B13
%B1 = udiv i177 %B5, %B6
%C9 = icmp ult i177 %Y, %B22
store i1 %C9, i1* undef
ret i177 %B1
}